The present invention relates generally to motors, and more particularly to harmonic motors.
Motors include harmonic motors. One type of harmonic motor has a rotatable rotor and a surrounding nonrotatable stator. The rotor makes a single point of contact with the inner circumference of the stator. The single point of contact rotates around (i.e., rolls around) the inner circumference of the stator. The rotor rotates a few degrees about its longitudinal axis for each complete rotation of the single point of contact about the inner circumference of the stator. In one modification, the outer circumference of the rotor and the inner circumference of the stator have gear teeth. Such motors find use in high torque, low speed motor applications. In one known variation, the rotatable rotor is above a nonrotatable stator, the rotatable rotor flexes or wobbles downward to make a single point of contact with the stator, the single point of contact rotates around an xe2x80x9cinner circumferencexe2x80x9d of the stator, and the rotor rotates a few degrees about its longitudinal axis for each complete rotation of the single point of contract. In another type of harmonic motor, a shaft is surrounded by a shaft driving member which is brought into a single point of contact with the shaft by electro-restrictive devices, wherein the rotor rotates a few degrees for each complete rotation of the single point of contact around an inner circumference of the shaft driving member.
Harmonic drive gear trains are known. In one known design, a motor rotates a xe2x80x9cwave generatorxe2x80x9d which is an egg-shaped member which flexes diametrically opposite portions of the surrounding flex-spline gear which is inside an outer gear. As the diametrically opposite teeth of the flex-spline gear contact the teeth on the outer gear, the rotatable one of the gears rotates with respect to the nonrotatable one of the gears.
What is needed is a new type of harmonic motor which uses at least two points of contact to rotate the rotor.
In a first expression of the invention, a harmonic motor includes a first annular member, a second member, and a device for flexing the first annular member. The first annular member has a longitudinal axis, lies in a plane perpendicular to the longitudinal axis, and is flexible along a direction which lies in the plane. The second member is substantially coaxially aligned with the first annular member and lies in the plane. One of the first annular and second members is rotatable about the longitudinal axis, and the other of the first annular and second members is nonrotatable about the longitudinal axis. The flexing device flexes the first annular member into at least two spaced-apart points of contact with the second member and sequentially flexes the first annular member to rotate the at least two points of contact about the longitudinal axis which rotates the rotatable one of the first annular and second members about the longitudinal axis. The flexing device is nonrotatable about the longitudinal axis.
Several benefits and advantages are derived from the first expression of the invention. By using at least two points of contact between the first annular and second members, the rotatable one (i.e., the rotor) of the first annular and second members is being driven by at least two points of contact by the nonrotatable one (i.e., the rotor driving member) of the first annular and second members. Driving the motor with at least two points of contact provides a more robust and more smoothly operating motor than is provided by the prior art, as can be appreciated by the artisan.